1. Field of the Invention
The present invention relates generally to the field of devices and methods for installing geothermal closed loops in the ground.
2. Description of the Prior Art
Geothermal heating and cooling systems operate by exchanging heat between the constant temperature ground and a heat exchange medium circulated in a tube extending through the ground. In order to cool a building, heat within the building flows into the coolant medium within the tube extending from the building and through ground. The reverse is true when heating a building wherein heat from the ground flows into the heat exchange medium which is then circulated via the tube in the building with the heat flowing from the tube into the building.
The tube must be inserted into the hole drilled in the ground. In order to minimize the time and expense in inserting the tube, there is disclosed herein means for holding the tube to the drill rod as the drill is used to bore the hole in the ground. Once the hole is formed, the drill is pulled out of the hole leaving the heat exchange tube within the hole. A bearing and bracket located on the drill allows the tube to remain in a non-rotating status even though the drill is rotating into the ground. In order to further minimize rotation of the tube that might be caused by rotation of the drill, a rudder is provided on the tube engaging the ground thereby limiting rotation of the tube.
In order to allow the rudder on the tube to stay in contact with the surrounding dirt, it is necessary to control the diameter of the hole being formed by the drill bit. The drill bit and associated drill rod components, must be of a certain size to enable the heat exchange medium holder along with its bearing and tube to extend freely into the bored hole while at the same time insuring that the rudder on the tube engages the side wall of the bored hole.
A sonde is located along the length of the drill and is operable to indicate the location of the drill bit within ground. For example, one such sonde housing is available from Vermeer Corporation of Pella, Iowa—Part No. 22686638001. Sonde housings are available in different diameters; however, in one geothermal application, it is desired to use the above-identified sonde housing having a relatively small diameter. The distal end of the sonde housing forms a drill bit mounting surface oriented at an angle relative to the axis of rotation of the drill thereby mounting the flat planar drill bit also at the same angle relative to the axis of rotation. The teeth at the distal end of the drill bit therefore project radially outward of the circumference of the sonde housing providing a larger than desired bored hole diameter. In order to eliminate this disadvantage, we have disclosed herein an adaptor, located between the drill bit and the sonde housing, having a beveled proximal end forming a mounting surface arranged at the same angle relative to the axis of rotation as the distal mounting surface of the sonde housing. The opposite proximal end of the adaptor is contained within a plane extending in the same direction as the axis of rotation thereby mounting the drill bit in the same plane ensuring that the drill bit does not extend further outward than the desired diameter of the hole. The bit includes a width which extends sufficiently outward to create a hole to accommodate the heat exchange tube and associated mount while enabling the tube rudder to engage the bored hole side walls limiting rotation of the tube even though the drill rod is rotating.
Once the heat exchange tube is inserted into the blind hole, it is desirable to hold or set the heat exchange tube within the hole. A flowable substance such as slurry is forced into the hole surrounding the heat exchange tube thereby securing the tube in place. A variety of flowable substances may be used. Typically, a thin mixture of insoluble material, such as cement, clay, coal, etc. with a liquid as water or oil.
The invention disclosed herein includes forcing the slurry through a hollow drill rod having a heat exchange tube attached to the drill rod. The distal end portion of the drill rod includes a plurality of outlets in communication with the passage extending through the drill rod allowing the slurry to exit into the blind hole. A mount on the drill rod removably holds the heat exchange tube. As the drill rod is withdrawn from the hole, the heat exchange tube disengages the drill rod remaining in the hole and is surrounded by the slurry thereby holding the tube in place.